Past and present pressures on forest resources have led to a drastic decrease in the surface area of unmanaged forests in Europe. Changes in forest structure, composition, and dynamics inevitably ...lead to changes in the biodiversity of forest-dwelling species. The possible biodiversity gains and losses due to forest management (i.e., anthropogenic pressures related to direct forest resource use), however, have never been assessed at a pan-European scale. We used meta-analysis to review 49 published papers containing 120 individual comparisons of species richness between unmanaged and managed forests throughout Europe. We explored the response of different taxonomic groups and the variability of their response with respect to time since abandonment and intensity of forest management. Species richness was slightly higher in unmanaged than in managed forests. Species dependent on forest cover continuity, deadwood, and large trees (bryophytes, lichens, fungi, saproxylic beetles) and carabids were negatively affected by forest management. In contrast, vascular plant species were favored. The response for birds was heterogeneous and probably depended more on factors such as landscape patterns. The global difference in species richness between unmanaged and managed forests increased with time since abandonment and indicated a gradual recovery of biodiversity. Clearcut forests in which the composition of tree species changed had the strongest effect on species richness, but the effects of different types of management on taxa could not be assessed in a robust way because of low numbers of replications in the management-intensity classes. Our results show that some taxa are more affected by forestry than others, but there is a need for research into poorly studied species groups in Europe and in particular locations. Our meta-analysis supports the need for a coordinated European research network to study and monitor the biodiversity of different taxa in managed and unmanaged forests.
Building a network of interconnected overmature forests is crucial for the conservation of biodiversity. Indeed, a multitude of plant and animal species depend on forest structural maturity ...attributes such as very large living trees and deadwood. LiDAR technology has proved to be powerful when assessing forest structural parameters, and it may be a promising way to identify existing overmature forest patches over large areas. We first built an index (IMAT) combining several forest structural maturity attributes in order to characterize the structural maturity of 660 field plots in the French northern Pre‐Alps. We then selected or developed LiDAR metrics and applied them in a random forest model designed to predict the IMAT. Model performance was evaluated with the root mean square error of prediction obtained from a bootstrap cross‐validation and a Spearman correlation coefficient calculated between observed and predicted IMAT. Predictors were ranked by importance based on the average increase in the squared out‐of‐bag error when the variable was randomly permuted. Despite a non‐negligible RMSEP (0.85 for calibration and validation data combined and 1.26 for validation data alone), we obtained a high correlation (0.89) between the observed and predicted IMAT values, indicating an accurate ranking of the field plots. LiDAR metrics for height (maximum height and height heterogeneity) were among the most important metrics for predicting forest maturity, together with elevation, slope and, to a lesser extent, with metrics describing the distribution of echoes' intensities. Our framework makes it possible to reconstruct a forest maturity gradient and isolate maturity hot spots. Nevertheless, our approach could be considerably strengthened by taking into consideration site fertility, collecting other maturity attributes in the field or developing adapted LiDAR metrics. Including additional spectral or textural metrics from optical imagery might also improve the predictive capacity of the model.
This paper deals with the potential of LiDAR technology to identify patches of overmature forest stands at the landscape scale. We first characterized the structural maturity of 660 forest field plots in the northern French Alps according to an index (IMAT) combining several forest structural maturity attributes. We then selected or developed LiDAR metrics and applied them in a random forest model designed to predict the IMAT and evaluated the model’s performance. We obtained interesting results showing that LiDAR technology makes it possible to reconstruct a forest maturity gradient and isolate maturity hot spots, as a first step to build an ecological network that is crucial for forest biodiversity conservation.
To more thoroughly explore the relative effects of forest continuity and maturity on biodiversity, 70 sites were selected in the Prealps in a cross-section of ancient and recent forests (defined by ...whether the land has been occupied by a forest for more than 150 years or not) populated by immature stands (small diameter trees and little deadwood) or very mature ones (large girth trees and plentiful deadwood). At each site, forest continuity and maturity were determined and four taxonomic groups were inventoried: vascular flora, epiphytic macrolichens, springtails and saproxylic beetles. Results point to a very slight legacy effect deriving from past uses as opposed to a strong effect from maturity. This limited forest continuity effect, compared to previous studies, is related to the ecological, landscape and historical contexts of montane forests: high percentage of forest cover, low level of fragmentation, high proportion of ancient forests, cropping history with little impact and extensively managed forests. Our results underline that the forest continuity effect on biodiversity must be better studied in context.
Afin de préciser les effets relatifs de l’ancienneté et de la maturité sur la biodiversité, 70 sites ont été sélectionnés dans les Préalpes croisant des forêts anciennes et récentes (le sol est occupé par une forêt depuis plus de 150 ans, ou non) avec des peuplements peu matures (arbres de petits diamètres et bois morts peu présents) ou très matures (arbres de gros diamètres et bois morts très présents). Pour chaque site, l’ancienneté et la maturité ont été caractérisées et quatre groupes taxinomiques ont été inventoriés : flore vasculaire, macrolichens épiphytes, collemboles et coléoptères saproxyliques. Les résultats indiquent un effet d’héritage dû aux usages passés très faible mais un effet fort de la maturité. Cet effet limité de l’ancienneté, comparativement aux études antérieures, est à mettre en relation avec le contexte écologique, paysager et historique des forêts de montagne : fort taux de boisement, forte proportion de forêts anciennes, faible fragmentation, antécédent cultural peu impactant et gestion forestière extensive. Nos résultats soulignent que l’effet de l’ancienneté sur la biodiversité doit être mieux contextualisé.
•We compared microhabitat densities between managed and strict forest reserves.•Microhabitat densities were higher in strictly protected than in managed forests.•Snags and large trees drove this ...difference.•The density of most microhabitat types increased with time since last harvesting.•This study may inspire biodiversity-friendly forest management methods.
Tree microhabitats (cavities, conks of fungi, bark features) play an important role for both rare and specialized species biodiversity; their preservation should therefore be targeted by biodiversity-friendly forest practices. However, when compared to other old-growth characteristics like deadwood or large trees, tree microhabitats have only recently been studied so related scientific knowledge is still relatively limited. Defining target values for microhabitat densities in managed forests is mostly based on expert knowledge rather than quantitative empirical data.
We compared the densities of microhabitat-bearing trees between managed forests, where wood is still harvested, and strictly protected forest reserves, where harvesting has been abandoned, in 17 French forests (222 plots) located in both lowlands and mountain regions. We found that microhabitat densities are generally higher in strict forest reserves than in managed forests and that this difference is mainly driven by standing dead and large living trees. Though scarce, standing dead trees over-contribute to the difference observed while large trees played a lesser but significant role. In addition, contrary to results obtained for other old-growth characteristics (such as deadwood volumes), the difference between managed and strict forest reserves was higher in mountain than in lowland forests. For individual microhabitats, five out of eleven microhabitats in mountains and only one in lowland (woodpecker cavities) were significantly more numerous in strict forest reserves than in managed forests. Finally, total microhabitat density and density of specific microhabitats such as cavities and bark features increased with time since the last harvest. This increase was also mainly supported by standing dead microhabitat-bearing trees. Compared to previous studies in comparable contexts, the densities we estimated were generally higher; however, such comparisons could only be made for the most documented microhabitat types.
Our results support the idea that management abandonment favours the abundance and diversity of microhabitats. However, microhabitat dynamics remain poorly known and only long-term monitoring will help understand underlying mechanisms of recruitment. In the meantime, our results may inspire forest managers in their application of daily biodiversity-friendly practices.
•We compared structure and deadwood in 17 managed and unmanaged French forests.•We showed that management abandonment favoured old-growth forest attributes.•Mean quantities of old-growth attributes ...were lower than for comparable European references.•This study constitutes a first reference for French forests at the national scale.
Over the past centuries in Western Europe, the long history of forest management has shaped both landscape- and local-scale forest structures. In France, a network of strict forest reserves was created in the 1950s to serve as a reference for nature conservation and forest dynamics. However, few studies to date have quantitatively compared the structural characteristics between managed stands and the reserves, where management has been (more or less recently) abandoned. In addition, the time needed for old-growth characteristics to restore themselves in strict forest reserves remains poorly known.
We analysed the differences in stand characteristics between managed and unmanaged stands in 17 French forests (233 plots) located in both lowland and in mountainous regions. We quantitatively showed that overall basal area, very large trees and deadwood features were significantly higher in unmanaged forests, though this pattern was mainly found in the lowland forests while in mountainous regions, managed and unmanaged forests showed far fewer differences. In addition, most structural characteristics that were higher in unmanaged forests also increased with the time since last harvesting.
Compared to the remaining old-growth forests elsewhere in Europe, the strict forest reserves in France often appear less mature, since they are still recovering from centuries of intensive management. Our results also show lower levels than those observed in other European studies on the restoration of old-growth characteristics over time; this indicates that it will take French reserves a very long time to reach values comparable to old-growth references in Europe. Our study constitutes one of the first references on unmanaged forests in France and may serve practitioners in their everyday management.
Old-growth forests provide a broad range of ecosystem services. However, due to poor knowledge of their spatiotemporal distribution, implementing conservation and restoration strategies is ...challenging. The goal of this study is to compare the predictive ability of socioecological factors and different sources of remotely sensed data that determine the spatiotemporal scales at which forest maturity attributes can be predicted.
We evaluated various remotely sensed data that cover a broad range of spatial (from local to global) and temporal (from current to decades) extents, from Airborne Laser Scanning (ALS), aerial multispectral and stereo-imagery, Sentinel-1, Sentinel-2 and Landsat data. Using random forests, remotely sensed data were related to a forest maturity index available in 688 forest plots across four ranges of the French Alps. Each model also includes socioecological predictors related to topography, socioeconomy, pedology and climatology.
We found that the different remotely sensed data provide information on the main forest structural characteristics as defined by ALS, except for Landsat, which has a too coarse resolution, and Sentinel-1, which responds differently to vegetation structure. The predictions were quite similar considering aerial remotely sensed data, on the one hand, and satellite remotely sensed data, on the other hand. Socioecological variables are the most important predictors compared to the remote sensing metrics.
In conclusion, our results indicate that a wide range of remotely sensed data can be used to study old-growth forests beyond the use of ALS and despite different abilities to predict forest structure. Accounting for socioecological predictors is indispensable to avoid a significant loss of predictive accuracy. Remotely sensed data can allow for predictions to be made at different spatiotemporal resolutions and extents. This study paves the way to large-scale monitoring of forest maturity, as well as for retrospective analyses which will show to what extent predicted maturity change at different dates.
•Old-growth forests provide a variety of ecosystem services.•Knowledge about their spatial and temporal distribution is very scarce.•We show how available remotely sensed data sources can fill this gap.•Our results pave the way to large-scale spatiotemporal predictions.
Long temporal continuity in forests has been shown to influence biodiversity through dispersal and recruitment limitations. However, for motile taxa that depend on stand maturity attributes, these ...limitations may be less relevant. Moreover, while certain habitats may be created rapidly, the development of other habitats may take a long time. Forest continuity and stand maturity may therefore have additive effects on biodiversity. Understanding their relative influence on biodiversity is crucial for conservation. We explored the response of species and functional trait composition of saproxylic beetle assemblages using a balanced sampling design in which we crossed forest continuity (ancient vs recent) and stand maturity (mature vs overmature). We established forty plots in montane forests where we sampled beetles. Stand maturity, related to deadwood resources, induced a strong environmental filtering on both species and functional trait composition. Regardless of forest continuity, species preferring large wood of late decay stages were more abundant in overmature stands. Moreover, overmature stands enhanced the co-occurrence of different saproxylic beetles with contrasting resource requirements. Forest continuity interacting with stand maturity induced taxonomic and functional changes in communities. Compared to other forest types, overmature stands in ancient forests hosted assemblages with many more characteristic species, with a larger average body size and species that prefer large deadwood pieces. Finally, a greater diversity of body sizes was found in these forests. Saproxylic species conservation should therefore benefit from strategies that favor setting-aside overmature stands in ancient forests, promoting sites with higher amounts and heterogeneity of deadwood.
•Stand maturity rather than forest continuity shaped assemblage structures.•Forest continuity interacts with stand maturity in providing valuable habitats.•Ancient-overmature stands hosted species preferring large decayed deadwood.•Large-bodied species were more abundant in ancient-overmature stands.•Conservation policies should chiefly focus on overmature stands in ancient forests.
Aim: Human activity is known to greatly influence species occurrences. In forest ecosystems, biodiversity is often believed to be influenced by two habitat characteristics: (1) forest continuity, ...related to a minimum length of time in a wooded state since a threshold date; and (2) stand maturity, related to the availability of late-developmentalforest attributes. In a context of ongoing global biodiversity loss, qualifying the effect of past and present human activity on forest ecosystems while taking into account variations in abiotic factors is of primary importance for conservation. Location: Temperate mountain forests in the Northern Alps. Method: Based upon a sampling design crossing forest continuity (ancient vs. Recent) and stand maturity (mature vs. overmature), and while controlling for the effect of two major environmental factors, soil and climate, we explored the individual response of saproxylic beetle, springtail, herbaceous plant and epiphytic macrolichen species to past and present human activity. Results: Forest continuity influenced the occurrence of relatively few species, indicating that past land use had almost no legacy effect on the species occurring in the study forests today. In contrast, stand maturity had an overall positive effect on species occurrences. However, our results showed that species occurrences were more obviously influenced by abiotic conditions. Indeed, beyond the effect of continuity and maturity factors, the probability of presence of numerous species was best explained by climate and soil. Main conclusions: Overall, we show that species occurrence was more influenced by stand maturity than by forest continuity, but also that site-specific characteristics were of great importance in explaining the probability of presence for numerous species. In the ecological context of alpine forests, these findings emphasize the need to better control for climatic and edaphic conditions in order to (1) improve accuracy in predicting species occurrence and (2) better design areas of conservation interest.
Do not drop OLD for NEW Janssen, Philippe; Bergès, Laurent; Fuhr, Marc ...
Frontiers in ecology and the environment,
09/2019, Letnik:
17, Številka:
7
Journal Article
Recenzirano
To assess forest conservation value, a focus on forest-cover continuity over time rather than tree age is proposed. A region-specific lists of lichens were recommended to be used as bioindicators of ...forest continuity. However, the way in which defined forest continuity was defined could be misleading, especially for forest managers and conservation biologists. The use of similar terminology to describe two concepts that not only influence biodiversity in different ways but also are crucial to disentangle for conservation purposes is also cited.
Aim
Human activity is known to greatly influence species occurrences. In forest ecosystems, biodiversity is often believed to be influenced by two habitat characteristics: (1) forest continuity, ...related to a minimum length of time in a wooded state since a threshold date; and (2) stand maturity, related to the availability of late‐developmental‐forest attributes. In a context of ongoing global biodiversity loss, qualifying the effect of past and present human activity on forest ecosystems while taking into account variations in abiotic factors is of primary importance for conservation.
Location
Temperate mountain forests in the Northern Alps.
Method
Based upon a sampling design crossing forest continuity (ancient vs. Recent) and stand maturity (mature vs. overmature), and while controlling for the effect of two major environmental factors, soil and climate, we explored the individual response of saproxylic beetle, springtail, herbaceous plant and epiphytic macrolichen species to past and present human activity.
Results
Forest continuity influenced the occurrence of relatively few species, indicating that past land use had almost no legacy effect on the species occurring in the study forests today. In contrast, stand maturity had an overall positive effect on species occurrences. However, our results showed that species occurrences were more obviously influenced by abiotic conditions. Indeed, beyond the effect of continuity and maturity factors, the probability of presence of numerous species was best explained by climate and soil.
Main conclusions
Overall, we show that species occurrence was more influenced by stand maturity than by forest continuity, but also that site‐specific characteristics were of great importance in explaining the probability of presence for numerous species. In the ecological context of alpine forests, these findings emphasize the need to better control for climatic and edaphic conditions in order to (1) improve accuracy in predicting species occurrence and (2) better design areas of conservation interest.
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